### P0420 Catalyst System Efficiency Below Threshold
– Typical Sources:
Faulty oxygen sensor [1]
– Common Solutions:
Diagnose fuel trim https://carautorepair.site/
### P0171 Air-Fuel Ratio Error
– Likely Problems:
Faulty MAF sensor
– Diagnostic Steps:
Smoke test intake [1][7]
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## Vehicle Service Vocabulary
### ABS (Anti-Lock Brake System)
– Purpose: Enables safe braking [7]
### Engine Management Unit
– Responsibility: Monitors sensors [7]
### Powertrain Elements
– Includes: Differential [7]
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## Mechanical Fixing Workflow
1. **Initial Diagnosis**:
Scan DTCs
2. **Component Testing**:
Check voltage
3. **Defective Unit Swap**:
Follow torque specs
4. **Final Quality Check**:
Confirm warning light reset
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## Essential Tools
| **Tool Type** | **Examples** | **Purpose** |
|—|—|—|
| Diagnostic Scanner | Innova | Live data streaming |
| Hand Instruments | Torque wrench | Electrical testing |
—
## Technical Data Resources
### Mechanical Information System
– Features:
TSB access [8]
Factory repair procedures
### Smartphone Tools
– Auto Repair Documents:
ECU pinouts [5]
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## Cost-Saving Tips
– Regular maintenance extends vehicle life
– Understand DTC meanings to avoid unnecessary repairs
– Select certified components when OEM prices prohibitive [7]